The present invention relates to a sealed, pressurized container for cooking gas for a stove, and more particularly, but without limitation to, a container for dispensing butane, or other flammable liquefied gasses including blends of the common hydrocarbon fuel gasses, to a cook stove. Although the present invention is described in connection with a container for containing and dispensing butane, it is applicable to other liquefied flammable gaseous fuels that may be used in a cook stove, or the like, for fueling a flame, primarily a cooking flame, but the invention is not limited to liquefied gaseous fuel for a stove.
A butane dispensing container or can contains liquid butane that is under pressure to maintain its liquid phase. The quantity of liquid does not completely fill the container so that the container has a vapor pocket above the liquid which, of course, enlarges as the fuel is dispersed. The fuel is provided to a stove as gas received from the vapor pocket. A vapor outlet tube extends from the vapor pocket, typically through the lid of the container, past a dispensing valve and to a burner where it is ignited.
A typical butane supply can is oriented horizontally in use in a stove, with its lid at one end. A vapor outlet tube passes through the lid, and one end of the tube extends into the container. An entrance into the one end of the tube is oriented toward the upper side of the horizontal container, since the vapor pocket will form at the top of the horizontal container. The vapor outlet tube passes through a channel through the lid. The outlet is controlled by a valve that is normally closed and that is openable to permit exit of vapor through the outlet tube and the channel to a fuel burner nozzle.
A conventional locating collar on the container at the lid or on the valve cooperates with a fixture, which is located on a stove where the container is installed, to cause an orientation of the container wherein its vapor outlet tube entrance is vertically up extending into the vapor pocket. The pressurized vapor is forced out through the outlet tube and the channel past the valve to the burner. If the butane fuel container is intended to be installed at an orientation other than horizontal, the placement of the entrance of the vapor outlet tube in the container is accordingly adjusted to be in the vapor pocket above the surface of the liquid pool.
Currently used, non-refillable, butane cans or containers are conventionally of three piece construction (or specialized, heavy wall, one or two piece construction). Conentional three piece cans include a can side wall with a welded vertical side seam, a separate seamed on or welded bottom and a separate seamed on or welded lid. Any of these three seamed areas or welds may leak or burst. The burst strength of a can is controlled by the tensile strength of the material used, its thickness, the can diameter and height and the weakness of any seams or welds. Reducing the number of seams obviously reduces the danger of leakage or bursts. Since there are conventional can diameters and can heights for fuel containers used in cookers, the containers must be sized to standard specifications.
Control over can wall thickness is important. Obviously, the wall must be thick enough not to burst under the pressures that may develop in the can, e.g. from severe heating, possibly caused by storage in summer heat. Consequently, the material of the can wall, its tensile strength and the thickness of the can wall are coordinated with the standard diameter for the can and with the pressure which is expected to develop in the can upon pressurizing the butane fuel to a particular level and upon the normal range of temperatures to which such cans may be exposed.
A major cost of a filled butane fuel can or container is the cost of the metal can itself, including the cost of materials and the cost of manufacture. Use of less material through thinner can walls and reducing the number of seams to be formed or welded should make can manufacture less expensive.
Further, all cans or containers from which butane fuel is exhausted should be disposable. There is an explosion danger with pressurized fuel. The cap of the container or can has a release valve for releasing any pressure remaining in the can before disposal of the can. The pressure may also be released in any other known manner for pressurized cans. Of course, a recycler receiving a standard rigid wall butane container would not be able to know if the can had been depressurized before it was given to the recycler. For safety, the recycler may have to depressurize the can to be sure it would not explode, at considerable labor cost.
A conventional, non-refillable, cylindrical shape, butane fuel container has a thick side wall, perhaps 0.009-0.010 inch steel, and the container is assembled from three parts. After the contents of the container have been fully exhausted, for practical purposes, the can still retains butane vapor. In the case of the most common size of butane cooking gas container, there would be approximately 520 millileters of butane gas at or slightly above atmospheric pressure remaining in the can. The standard can wall remains so rigid when the can is emptied that the can cannot be easily crushed by normal adult hand pressure or even be deformed by normal adult finger pressure. It is therefore dangerous and may be difficult to recycle the can, except in an explosion proof recycling apparatus or after individual attention to the can to surely depressurize it. As noted, the typical can has a means to manually release the residual pressure, so that the user of the can may exhaust its contents to reduce any explosive hazard. But the recycler receiving such a can would not know and could not determine during simple handling of the can if the can pressure had been reduced to a level where the explosion danger had been virtually eliminated.
It is a primary object of the invention to provide a container or can for a pressurized burner fuel, which is light in weight, inexpensive for materials and manufacture, as compared with conventional fuel supply containers or cans, is disposable with clear indication that it is safe for disposal, is crushable after use, if the user wishes, and which may improve the efficiency of the burner supplied by the fuel.
According to the invention, the fuel supply container or can, particularly the butane can, is a two piece can formed in a cold forming drawing and ironing process. The drawing and ironing process provides a bottom and a side to the can, so that no welds or seams are present from the bottom to the can or along the side of the can. A top or lid having a dome shape is seamed or welded on the open end of the can. The process may be also performed in reverse by forming the lid integrally with the side walls and then attaching a bottom. The container is preferably formed of steel. The forming process increases metal strength so it permits a thinner can wall. A one-piece container can also be made by first forming the bottom and sides by the drawing and ironing process and then necking in the upper portion of the side walls to form a top or the lid for the container with an opening for the valve.
The side wall of the butane container of the invention is thinner than side walls of conventional butane containers. The can side wall is of such material and is thin enough for the can diameter and height that the can side wall can be deformed with ease, when the can is depressurized by normal finger pressure of a typical adult of 5 pounds force and the can can be crushed by normal hand pressure of that typical adult of 20 pounds force when the pressure release valve of the can is held open and such finger or hand pressure is applied to the can by the typical adult. In other words, the can is soft or deformable to the touch when depressurized, but is rigid to the touch while it still retains pressure. This gives anyone, consumer or recycler, who touches the can, an immediate tactile indication of whether or not the can has been depressurized and is safe for disposal.
For a recycler, the benefit of knowing that a can is safe for disposal, without having to test it or depressurize it to be certain, provides a saving in effort. The xe2x80x9cfinger pressurexe2x80x9d deformation test, the simple tactile sensation of deformability by a person""s fingers holding the can, even without the person having to actually deform the can, provides a simple test of whether a can is depressurized. It is an important, yet simply performed safety test, particularly before recycling the can.
For example, the wall of a steel can according to the invention might be 0.002-0.006 inch and preferably 0.005 inch thick, rather than the conventional steel wall for such a can, which is 0.009-010 inch. Correspondingly, an aluminum can wall would have a thickness selected dependent upon the alloy material selected for the can wall, the pressure in the can and the can diameter, since a smaller diameter can would provide a stronger wall for a particular wall thickness than a larger diameter can.
There are additional benefits to this can design. As vapor is expelled through the can outlet to the burner, there is a drop in temperature of the liquid and a corresponding drop in pressure of the vapor at the valve and at the final outlet from the can due to the vaporization of the liquid butane, and the resultant flame fueled by the vapor becomes somewhat smaller and may cook less effectively. A thinner side wall of the can is a better heat conductor than is a thicker wall. The heat of the burner may heat the vapor tube leading from the container and may heat the container as well. The ambient heat of the environment will also heat the container. The heat from both of these sources is conducted into the butane container better by a thinner side wall than by a thicker wall, thus keeping the butane contents at a slightly higher temperature and improving the resultant flame produced at the burner. If the side wall of the can is a better heat conductor, there is less of a pressure drop in the can due to the cooling from vaporization, so better vaporization and more vapor pressure is generated.
In contrast to a rigid container, for which a recycler would not be able to determine, from looking at the can, whether it had been depressurized, when the thin walled can of the present invention is crushed after opening at the valve and exhausting its contents, this would provide a clear indication that the can has been depressurized and that it may be safely disposed of or recycled. In the event that the can has been depressurized but not crushed, the consumer or recycler can easily determine by simply squeezing the can whether or not it has been depressurized. If it is soft to the touch, it has been depressurized and is safe to recycle. If it is rigid, it has not been depressurized and presents a hazard if recycled.
Other objects and features of the invention will become apparent from the following description of a preferred embodiment considered in conjunction with the accompanying drawings.